[PATCH 0/2] powerpc/xive: fix CPU hot unplug

[Cédric Le Goater]

>>> I haven't yet because I fail to understand why the decrementer is not 
>>> interrupting the dying CPU under xics as it is the case under XIVE.
>>
>> Oh.. ok.  This sounds very similar to the problem Nikunj hit under TCG
>> with decrementer interrupts waking up a supposedly dead CPU.  He had a
>> couple of proposed fixes, but we got bogged down trying to work out
>> why  (with TCG at least).
> 
> Yeah, I wasnt able to get to the exact reason for that.

Yes. Tracking all the CPU states is a nightmare.

 * @running: #true if CPU is currently running (lockless).
 * @has_waiter: #true if a CPU is currently waiting for the cpu_exec_end;
 * valid under cpu_list_lock.
 * @created: Indicates whether the CPU thread has been successfully created.
 * @interrupt_request: Indicates a pending interrupt request.
 * @halted: Nonzero if the CPU is in suspended state.
 * @stop: Indicates a pending stop request.
 * @stopped: Indicates the CPU has been artificially stopped.
 * @unplug: Indicates a pending CPU unplug request.


I will spend some more time to understand why XICS is not behaving 
the same. This is really time consuming ...

C.